Former world lightweight champion Leavander Johnson died in hospital on Thursday, five days after suffering brain damage in a title bout in Las Vegas.
The 35-year-old American collapsed while heading to his dressing room after he was stopped in the 11th round of a failed IBF lightweight title defence against Mexico's Jesus Chavez on Saturday.
Johnson was rushed to hospital with bleeding on the brain, where doctors performed emergency surgery, but he never regained consciousness from a medically-induced coma.
His kidneys had failed and his heart had stopped beating when it was decided to remove him from life support.
Hospital officials said family members were present when the boxer passed away and they had made the decision to remove the life support systems earlier in the evening.
Johnson's father was his trainer and his brother was his manager.
Born in Atlantic City, New Jersey, Johnson spent 16 years as a professional boxer and finally won the 135-pound division title in June, but was punished by Chavez in his first defence before the referee stopped the contest.
He managed to walk from the ring on his own but began to struggle as he got closer to the dressing room.
He was taken immediately to University Medical Center for the emergency surgery and a second operation was performed on Monday but there was too much damage to allow him to survive.